1.
The invention relates generally to earth drilling apparatus and, more particularly, but not by way of limitation, it relates to an improved drilling apparatus which utilizes a force accumulator to enable continuous drill progression.
2.
There are various forms of prior art drilling device which are driven either hydraulically, electrically or pneumatically to provide borehole formation in and around mines. One type of drilling apparatus which should be noted is a device manufactured by Drilco Corporation of Midland, Texas which consists essentially of a hydraulic piston functioning in coaction with two sets of borehole wall anchors, as alternately actuated, to progress by intermittent operation through the earth formation. The device operates by pressuring one set of borehole wall anchors to engage the wall, and increasing pressure on the piston to drive the piston forward to force the drill stem. When the piston has reached its limit, a second set of anchors is pressurized forcing them against the borehole wall while the original set of borehole anchors is disengaged, and the piston assembly is then retracted to a new position as anchored by the second set of anchors, whereupon the first set of anchors is then repressurized and the second set of anchors is retracted, and the process is carried out repeatedly. The drill progression is intermittent because the retracting of the piston allows no pressure to be applied to the drill, thus reducing the drill time by the time required to retract the first set of anchors and move the piston and anchor assembly to the next location. Finally, additional prior art of note is U.S. Pat. No. 3,827,512 entitled "Anchoring and Pressuring Apparatus for a Drill" as patented on August 6, 1974 in the name of Tibor O. Edmond and owned by the present assignee.